• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.46-49
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• 2022

Since CORC^®(Conductor on Round Core) is made of multiple strands of a superconducting tape to conduct a large current, it is difficult to measure the critical current due to the limitation of a capacity of a power supply. The magnetization loss of a superconductor is dependent on the full penetration field. The full penetration field corresponds to the inflection point of the magnetization loss graph with respect to the external magnetic field. We propose a method to predict the critical current of CORC^® indirectly. This method uses the measured magnetization losses of various CORC^® samples for the prediction of the critical currents.

• 한국진공학회지
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• 제16권4호
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• pp.262-266
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• 2007

Mn 치환이 역스피넬 산화물 $Fe_3O_4$에 미치는 영향을 조사하기 위하여 졸겔 스핀코팅 방법을 이용하여 다결정 $Mn_xFe_{3-x}O_4$ 박막을 Si(100) 기판 위에 제작하고 그 구조적, 자기적, 자기저항특성들에 대한측정 및 분석을 수행하였다. X-선 회절 측정 결과, Mn 성분비가 증가함에 따라 x = 1.78까지 입방 구조를 유지하며, 그 격자상수는 증가함을 나타내었다. 이와 같은 격자상수 증가의 주된 원인으로 사면체 자리를 선호하는 $Mn^{2+}$ 이온이 이온반경이 상대적으로 작은 사면체 자리의 $Fe^{3+}$ 이온을 치환함에 의한 것으로 해석된다. 박막들에 대한 진동시료자화 측정 결과, Mn 성분비 증가에 따라 포화자화량은 큰 변화를 나타내지 않았는데, Mn과 Fe 이온들의 스핀 자기능률 값 비교를 통하여 그 정성적인 설명이 가능하다. 반면 Mn의 농도가 증가함에 따라 보자력은 감소하였는데, 이는 $Mn^{2+}$ 치환에 의한 $Fe^{2+}$ 이온 농도의 감소에 따르는 자기 이방성의 감소에 기인하는 것으로 해석된다. 자기저항 효과측정 결과, Mn 성분비 증가에 따라 감소하는 경향을 보였으며, 자화 의존도 변화와 비교분석 결과 다결정 $Mn_xFe_{3-x}O_4$ 박막 시료들에서 나타나는 자기저항은 스핀분극된 carrier의 grain boundary tunneling 및 spin-flip 현상에 의한 것으로 해석된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.900-902
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• 1992

In order to develope the uniform Plasma source which is able to make polymer or glass surface modification, the d.c glow discharge characteristics for the hemisphere -cylindrical electrode system with external d.c magnetic field are investigated. Single probe method has been used for detecting plasma parameters. We make uniform plasma generated to the external of electrode between hemisphere and cylindrical electrode. The surface treatment of metal and insulate has been performed by this uniform plasma.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1741-1746
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• 2003

Effects of electromagnetic force which is one of the most important factor of metal transfer that affects bead geometry and microstructure of weld metal in GMAW(gas metal arc welding). In this paper, different ways of external electromagnetic forces were applied on GMAW process and their effects on the welding were studied. On certain conditions, better bead geometry, better influence on the arc and metal transfer mode and higher welding efficiency could be obtained. Experimental methods and their results will be presented.

• 한국진공학회지
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• 제5권1호
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• pp.85-92
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• 1996

The external electricla characteristics of helicon wave plasmas were measured over a wide range of RF power and magnetic filed. External parameters. such as antenna voltage , current, phase shift, and interanl parameter, electron density were measured at 7MHz, 1mTorr Ar discharge . The equivalent discharge resistance and reactance, and the power transfer efficiency were calculated through these measurements. There are a helicon mode which produces high density plasma by helicon wave and a lowmode which produces low density plasma by capaictive electric field. In case of the helicon mode, the anternna voltage and current were lower than those of the low-mode. The phase difference between voltage and current decreased suddenly at the transition point from the low-mode to the helicon mode. Equivalent resistance and power efficiency increased and reactance decreased suddenly at the transition point. These results mean that the power transperred to plasma and the nutual coupling between the antenna and plasma increase as the mode changes from the low-mode to the helicon mode.

• 한국초전도ㆍ저온공학회논문지
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• 제17권2호
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• pp.25-30
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• 2015

In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.149.1-149.1
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• 2007

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.626-631
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• 2007

MR(Magneto-rheological) fluid is smart material that can be changed viscosity by controlling the magnetic field. MR damper with MR fluid can control damping force. It can be used extensively many engineering structures for reducing the effect of dynamic external disturbances. There are three kinds of MR dampers, such as valve mode, direct-shear mode and squeeze mode. In this study, design process of direct-shear mode MR damper with the MR fluid gap was developed. The parameters that used in the direct-shear mode MR damper Informed from the experiment of valve mode MR damper of Lord company. Magnetic analysis with finite element method was performed to find the optimal annular gap.

• 한국자기공명학회논문지
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• 제16권1호
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• pp.11-21
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• 2012

The line-width of carbon nanotubes (CNTs) was studied as a function of the temperature at a frequency of 9.49 GHz in the presence of external electromagnetic radiation. The relative frequency dependence of the absorption power is obtained with the projection operator technique (POT) proposed by Kawabata. The line-width increased as the temperature increased in the high-temperature region (T>200 K). The scattering is little affected in the low-temperature region (T<200 K) because there is no correlation between the resonance field and the Fermi-Dirac distribution function. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition problems.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.98-102
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• 2009

The magneto-rheological fluid expresses different cohesiveness according to the strength of the external electric current. To manufacture the magneto-rheological fluid damper that uses such characteristics of the fluid, a flow analysis of the inner damper was conducted to forecast the damper's capacity. In addition, using the finite element method software, analysis on the characteristics of electromagnetic field around the coil operation unit inside the damper. Based on the result of the analysis, a single core damper and a double core damper were built and tested for their dynamic function. Based on the result of the experiment, the propriety of the flow analysis was demonstrated, and the proposed model was verified.